Well, you can never travel back in time, but you can surely travel back time for about 1 day if you go to one country and another country with the time zone being 1 day back. You can have Christmas 2 times that way ! You can also travel back a few minutes in time if you surpass the speed of light, but who would want to travel a few minutes back in time? Lol. If you found a way to go back in time using a spaceship that goes 10 times the speed of light, then it would take you around 5 minutes to get in the spaceship, 5 minutes for launch, 5 minutes for getting to the speed of light, and that would be 15 minutes. At that time, when you're at the speed of light, then you will travel around 3 minutes back, when the spaceship would be getting to the speed of light, lol. But I don't really know, on Discovery they showed an animation about a dog and a cat, the cat was on earth, the dog was on a spaceship, the dog was going at the speed of light, and when he cam back down to earth, he was still healthy, but there was a sign saying R.I.P: Tiddles, the cat. But that theory, I think is not so correct, because you cannot get a spaceship that travels at the speed of light.